Part of the fiddling and experimentation with hydroponics is to learn as much as possible and to see if the hydroponic chemically based food can be replaced by an organic alternative. This is to avoid the cost of the chemicals as well as produce a more organically focused product. The complete switch across to a purely organic food (the fish water) has been tried before in aquaponic units but there is usually a problem with a lack of potassium, calcium iron and magnesium which has to be supplemented.(e- book “Alittleofeverythingaquaponic”-Henri Pereira 2015
The immediate concern with an aero-ponic unit (as opposed to alternatives like Nutrient Film Technique (NFT) or individual pot drippers) , is the blockage of any fine nozzles.We are simultaneously experimenting with a filtration system to address this. Despite this shortcoming, the original interest in this unit stemmed from it being compact and lightweight and the possibility of running several on the flat roof structure where we were residing at the time.
The way forward definitely involves a deep water culture system with air pump feed and a polystyrene floating island as it is very appealing in terms of simplicity and robustness and weight is no longer such a big issue. It also offers an alternative methodology which we need to try for suitability. Thereafter we would also like to try drip irrigation fed individual pots but for that we will need our hoop house structure to have been put in place.
The Build Concept
Like most projects endorsed and explained on the internet, the design flaws and general shortcomings really only come to the surface once you have built a prototype and tried running it. However, although there is a cost involved and a bit of work, those we choose also are a lot of fun and we try to keep costs to a minimum.
We decided on four grow-tubes, with five pots in each and a tap on each to be able to isolate the grow-tube if necessary. The design has the ability to open the tube to reach inside if necessary and is built on a frame which would support it’s own plastic dome, bird net and shade-cloth. The sump is a plastic container and a 12 volt bilge pump that fitted the budget and has the ability to be run off solar power. We will use individual bent risers and a small nozzle on one side of the pots to spray the roots. This may need to be boosted at a later stage to an additional riser and nozzle on the other side- time will tell. We won’t go into the control panel at this stage but have simply wired the pump in accordance with what was suggested with a three way switch. As it is a bilge pump it should not run continuously and so we have incorporated a timer to run short cycles all of which we will try optimize through trial and error.
For the support frame we used 40mm PVC pipes, elbows and tees and for the canopy we used 20mm conduit. As we are constantly evolving with the set up at mini Cradle Ark we did not glue everything so that we could disassemble to move the unit but this does lead to problems and irritation so ideally the structure should be glued. Size wise the unit does take up a fair amount of space but we are hoping that it will produce enough to justify that usage of space.
The basic measurements we used were as follows:
Longer legs 1000 mm
Short legs 90mm
Length of grow tubes 1540mm
Horizontal gap between grow tube 230mm (This is a bit tight when wanting to slip into the frame to work on a particular spray. 300mm would have been better)
Hole spacing (centre to centre 300mm)
Hole size 72mm (for the net pots that I had)
The support frame is assembled with the grow pipes held in place by two 110mm brackets at each end. This picture shows the lower side of the frame as the pipes need to drain back to the sump.
The holes for the net pots are then cut using a hole saw.
We made a simple bender for the consistent production of the risers. This was then used with the help of a heat gun to produce the risers.
The individual risers have been bent and added to the structure. The plumbing of the food feed has now been started.
The other side has threaded ends to allow access. The drainage and food feed with individual lines is shown above.
The plastic is added to the canopy using a glue gun as it makes it quick and effective to get the plastic into place and reasonably taught. We have also added bird netting and shade cloth to the structure.
We had to add two small (4mm) holes next to each spray .These were used to align the direction of the riser and sprinkler head and hold it in place with a small cable tie.
The sump is simply a plastic container with the outflow of the aeroponic unit leading into it and the food feed leading out of it.
The bilge pump, a CE 190 1100 GPH , is housed on a plastic board that is tapped and the pump held down and in place by two self- tapping screws. The wiring of the pump has a float switch on one side and a manual override on the other. I believe the float switch will be an effective mechanism to protect the pump but the manual override is wired in a three way switch.
The unit, in turn, is then wired to a short-cycle timer which then controls the watering process . We sourced an Orbit data Log (code OB174072) which is 12 volt and can run multiple short cycle programmes.